Chickenpox and Its Vaccine

November 10, 2008 By Vaccine Choice Canada

Incubation of chickenpox (also named varicella) takes 2-3 weeks. The first signs of the illness are usually a slight fever, headache, backache and loss of appetite. Then, after 1-2 days, the pox appear on the back and chest, then spread elsewhere, mostly on the trunk. As the fever rises, the pox spread for 2-3 days, first appearing like small red pimples, then blisters. The blisters break and form scabs which drop off after 1-2 weeks. Scarring is rare.

A person is most contagious from 1 to 2 days before to shortly after the onset of rash. Contagiousness persists until the skin lesions crust over. During this time, the patient should be kept isolated from individuals who have no immunity to chickenpox and are at risk of serious consequences if they become infected. Chickenpox in children rarely leads to complications and confers lifelong immunity to those who contract it. However, chickenpox in adults is often more severe and dangerous. And, just as for the use of mass immunizations against measles, mumps, rubella and pertussis, with continued mass immunization against chickenpox we can expect to see an epidemiological shift of the disease to older segments of the population.

Chickenpox vaccine requires careful storage and handling since it is sensitive to temperature and light. The 2007 VARIVAX® III Merck Frosst monograph admits, “no placebo-controlled trial was carried out with varicella vaccine using the current formulation of the vaccine”. The current formulation contains “a minimum of 1350 PFU (plaque forming units)” of live virus per dose after preparation and storage for 90 minutes. The placebo-controlled trial used to determine efficacy contained a whopping 17,000 PFU per dose! This trial was carried out for only two years and, even at that, “In the second year…only a subset of individuals agreed to remain in the blinded study”.

The monograph discusses “breakthrough cases” of chickenpox in up to 19.4% of trial subjects observed for up to nine years after being injected with one dose of various chickenpox vaccine formulations with PFUs per dose as high as 9000. However, the majority of these cases are said to have been “mild”, mild meaning that the greatest number of lesions occurring at any time during the illness was about 50. Regarding efficacy against chickenpox complications, the monograph states: “There is an insufficient number of breakthrough chickenpox cases in vaccinated children to assess the rate of protection of varicella vaccine against the serious complications of chickenpox (e.g., encephalitis, hepatitis, pneumonia).”

Merck Frosst acknowledges one of the benefits of not vaccinating against the illness. They note, “A boost in antibody levels has been observed in vaccinees following exposure to wild-type varicella which could account for the long-term persistence of antibody levels after vaccination…The duration of protection from varicella obtained using varicella vaccine in the absence of wild-type boosting is unknown.”

As well as the unknowns about efficacy, since this is a live virus vaccine, there is also the problem of vaccine-virus transmission. The monograph warns, “vaccine recipients should attempt to avoid, whenever possible, close association with susceptible high-risk individuals for up to six weeks…Susceptible high-risk individuals include: immunocompromised individuals; pregnant women without documented history of chickenpox or laboratory evidence of prior infection; newborn infants of mothers without documented history of chickenpox or laboratory evidence of prior infection.” [emphasis ours] The monograph nonchalantly remarks, “It is not known whether varicella vaccine virus is secreted in human milk. Therefore, because some viruses are secreted in human milk caution should be exercised if VARIVAX® III is administered to a nursing woman.” How, we ask, can there be caution after the risky procedure has already taken place? Concerning the possibility that mass vaccination using chickenpox vaccine will increase the incidence of herpes zoster, the virus associated with shingles, the monograph indicates, “The completeness of this reporting has not been determined.”